Fastener



June 6, 1939. A. v. BOGGILD FASTENER' Original Filed April 24, 1934Inventor. Axel \/.Bo ild, by JV His Attorneg.

Patented June 6, l939 General New York PATENT OFFICE noun 7 mama AxelBoggiid, Trumbull, Com, m: to Electric Company, a corporation ofOriginal application April 24. 1934. serial No.

Divided and this application Decembe!" 14, 1937, Serial No. 179,713

18 Claims.

This application is a division of my application Serial No. 722,078filed April 24, 1934.

The present invention relates to self-tapping screws or fasteners. I

In the manufacture of electric wiring devices, it has become a recentpractice to secure metal parts to parts of insulating material by aforce or drive' fit between the metal and the member of insulatingmaterial. This practice is of interest 10 because of its relatively lowcost as compared with the old practice of molding metal inserts in thepart of insulating material into which screws could be threaded tosecure a metal part to the member of insulating material. However, thispractice is not entirely satisfactory because there is a. tendency tobreak or fracture the member of insulating material frequently. Anotherpractice has been somewhat developed of late which consists in moldingor drilling an opening in the member of insulating material and thensecuring a metal part to it .bymeans of a tap screw which will cut itsown thread into the member of insulating material and will secure themetal part to it. This latter practice is quite satis- 15 factory exceptfor the relative high cost of the tap screw. The high cost of the tapscrew is due to the necessity-of first providing a thread on the screwand then milling longitudinal grooves in the screw to make the screwself-tapping.

The object of my invention is to provide a selftapping screw which maybe manufactured at no "greater cost than an ordinary screw and whichwill work efficiently and satisfactorily as a selftapping screw forsecuring metal parts to. mem- 33 bers of insulating material.

What I consider to be novel and my invention willbe better understood byreference to the following specification and appended claims whenconsidered in connection with the accompanying drawing.

Referring to the drawing, Fig; 1 is a plan view of an improved machinefor manufacturing self tapping screws; Fig. 2 is a perspective view ofthe dies mounted in the machine of Fig. 1; Fig.

5 3- is a perspective view of an insert located in one of the dies ofFig. 2 and Fig. 4 shows in perspective a self-tapping screw manufacturedin accordance with my invention.

By my invention a self tapping screw is provided which is manufacturedby rolling a thread and longitudinal grooves in the shank of the screwsimultaneously.

Referring particularly to Fig. 1, a reciprocating slide IQ carries a dieH which is held in the slide by means of a clamp l2. Clamp i2 may beloosened or tightened by means of stud i3. An adjustable holder Itcarries a stationary die l5 which is held in position by a clamp itwhich may be loosened or tightened by means of stud ll. In themanufacture of a screw, a rod or screw blank i3 is placed adjacent theright hand end of stationary die it. As the die ii moves to the leftwith reciprocating slide it, a starter rod i9 movesthe rod or screwblank I! to the left on the surface of die i5.. Rod i8 is then grippedby the moving die II and rotated across the face of die ii. In themovement of the rod across the face of die IS a thread is rolled on therod. In the movement of the die ii the rod I3 is rotated and so the diemoves faster than the rod, The right hand end of the moving die ii isshown in dotted lines just as the rod it, which is also shown in dottedlines, passes from the left hand end of die I5. The threaded rod orscrew blank I! then passes to a receiving receptacle which is notshownon the drawing. As better indicated in Fig. 2, dies ii and I5 areprovided with angular grooves 2|! and 2i respectively which form thethread on the rod l8 as it rolls between the two dies with the movementof die ii. To form longitudinal grooves 22 in the screw shown in Fig. 1to make the screw self-tapping, an insert 23 is provided in die II whichhas transverse grooves 24. Insert 23 is secured in a slot provided shankof the screw. When the portion of die ll carrying insert 23 firstengages the screw I8, the longitudinal grooves are formed in the shankof the screw. The grooves 2| in die l5 serve to clean up any deposit ofmetal or burs raised by engagement of the insert 23 with the screw itupon the continued relative movement of die H with respect to the screwl8 and die ii. In the movement of the screw l8 with respect to theinsert 23, the longitudinal grooves 22 are formed at spaced intervalscompletely around the circumference of the screw.v The number of thesegrooves 22 and their spacing is determined by the use to which the screwis to be placed and may be varied at will by the substitution of adifferent insert 23.

From the foregoing, it may be seen that a selftapping screw with 9.rolled thread and longitudinal grooves is, provided which may bemanufactured at no greater cost than the manufac ture of the ordinaryscrew.

Not only is the screw formed by the above method lower in cost but inactual use it has been found superior to prior art self-tapping screws.

For example, it can be threaded into thinner wall sections of modedinsulating material without breaking the walls. This is due to the factthat the ribs forming the threads and the intersecting grooves formingthe interruptions providing the abrupt shoulders or cutting edges arerolled from the material of the rod l8 during which process the fibersof the metal are not out or severed but are compressed, resulting inincreased density of the metal. The material forming the grooves 22 isnot cut away from the threads but is compressed during the rollingprocess into the body of the blank I8 and into the surrounding threads,so that the surfaces of the grooves 22 and the resulting edges on theends of the threads are smooth and free from burrs and have increaseddensity due to the compression of the metal. Since the fiber of themetal is not cut, the threads, andparticularly the cutting edges of thethreads adjacent the grooves, have increased strength and hardness. Thesimultaneous rolling of the threads and grooves also forms these cuttingedges without burrs.

By determining the grain structure of the metal, it is possible todetermine whether the threads and grooves have been formed by rolling orwhether the grooves have been formed by slotting, as in the prior art.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. In an article of manufacture a screw having a rolled thread androlled longitudinal grooves interrupting the threads. 7

2. A fastener comprising a body having 8. rolled thread thereon andintersecting rolled longitudinal grooves, providing cutting edges on thethread. v r

3. A fastener having a body provided with a thread and intersectinglongitudinal grooves, the metal forming the thread and grooves beingformed by rolling the fastener body between dies having projectionsfitting in the longitudinal and thread grooves and squeezing metal fromthe body to form the threads and grooves.

4. A fastener comprising a body having a.

thread and intersecting grooves simultaneously rolled thereon.

5. A fastener comprising a body and a thread thereon, the thread beingintersected by grooves extending along the body across the thread toprovide abrupt cutting shoulders and havingthe material of the threadand body along the surface of the grooves compressed and kneaded as bythe formation of the grooves by rolling.

6. A fastener comprising a. body and a thread thereon, the thread beingintersected by grooves extending along the body across the thread toprovide abrupt cutting edges, and the surfaces of the thread at thecutting edges being more compact than the other portions of the body, asby being compressed and intersected by a rolling operation.

'I. A fastener comprising a body having a thread thereon and groovesintersecting the thread and providing cutting edges formed with thematerial of the walls compressed and providing finished surfaces for theedges and unbroken fiber of the material of the body about the edges.

8. A fastener comprising a body having a thread anda groove intersectingthe thread and providing cutting edges formed with the material of thewalls compressed and providing finished surfaces for the edges andunsevered fiber of the material of the body about the edges.

9. A fastener comprising a body having an outstanding thread-like ribthereon having an interruption in its length providing cutting edges,the surfaces of the rib at the cutting edges being more compact thanother portions of the body as by being compressed and intersected by arolling operation.

10. A fastener comprising a body having an outstanding thread-like ribthereon having an interruption in its length providing cutting-edges,the material of the rib and body along its length and at the cuttingedges being compressed and kneaded as by rolling.

11. A fastener having a body provided with a thread-like rib having aninterruption in its length forming cutting edges, the metal forming therib and the interruption being formed by squeezing. the metal from thebody and the rib to form the rib and the interruption.

12. A fastener comprising a body having a thread-like rib thereon withan interruption in its length, the rib and the interruption beingsimultaneously rolled thereon.

13. A fastener comprising a. body having outstanding thread-like ribshaving interruptions in the length providing cutting edges, the materialdisplaced by the interruptions being compressed and flowed into the bodyand the edges of the ribs providing cutting edges of relatively densematerial.

14. A fastener comprising a body having outstanding thread-like ribshaving interruptions in the length providing cutting edges, theinterruptions being formed by rolling whereby the metal displaced iscompressed and flowed into the body and the edges of the ribs providingcutting edges of relatively great density.

15. A fastener comprising a body and a thread thereon, the thread beingintersected by grooves extending along the body across the thread toprovide abrupt cutting shoulders, the broken thread sections and thecutting shoulders having the characteristics of compactness andsmoothness produced by repeatedly subjecting the same parts alternatelyto thread pressing and groove broken thread sections and the cuttingshoulders having the characteristics of compactness and smoothnessproduced by repeatedly subjecting the same parts alternately to threadpressing and groove pressing operations.

18. A fastener comprising a body having an outstanding thread-like ribhaving an interrup-

